The Dignity rule is a rule of social evolution. It states that the more advanced a human society the more the dignity of its members, us humans, is respected.
This is a typical rule of social evolution as it can be observed over history. All the way fro slavery to democracy. In history human, dignity often is advanced by war a can be clearly demonstrated with the American and German history. By the American civil war which abolished slavery, and the lost WW2 which brought human dignity into the constitution.
Also as a typical rule of social evolution it applies to different societies within the period. The currently observed social differences among countries strongly correlate with the respected human dignity. At this point it is worth mentioning that democracy is only a proxy of respected human dignity which sometimes is overemphasized ideologically.